Brachymenium acuminatum together with B. exile and B. fabronioides are all very small plants and terrestrial, B. acuminatum and B. fabronioides have stem leaf costa percurrent to very short excurrent, whereas B. exile usually has a stoutly long excurrent costa; B. acuminatum has innovation leaves that are narrowly triangular to short ovate-acute, whereas B. fabronioides has at least some of the innovation leaves broadly ovate-acuminate.